With the CBS blackout entering its third week, calls for federal regulators' intervention and a quick settlement between the network and Time Warner Cable are growing louder as the NFL season gets underway.

U.S. Sens. Barbara Boxer and Dianne Feinstein, both California Democrats, sent a letter to the companies Monday, urging both parties to agree on a contract. "The status quo is unfair to the millions of your customers who are caught in the middle of your dispute, and we strongly encourage both sides to resolve it immediately," they wrote to TWC CEO Glenn Britt and CBS CEO Leslie Moonves.

CBS and TWC are in the midst of a retransmission contract dispute, resulting in the blackout of the No. 1 prime-time network in New York, Los Angeles, Dallas and several smaller markets.

The network went dark on Aug. 2 after the parties have failed to agree on a new contract that would spell out the amount of money CBS receives for its shows and other terms. They're also negotiating over the digital rights to shows that are streamed over the Internet.

Several consumer groups called for more involvement from federal regulators. In a statement, the National Consumers League, an advocacy group in Washington, D.C., said the squabble "should demonstrate to the Federal Communications Commission that it cannot simply leave this proceeding open and hope the problem solves itself. ... We urge acting FCC Chairwoman Mignon Clyburn and incoming Chairman Tom Wheeler to give this issue the time and attention it deserves."

Responding to a reporter last week, Clyburn said she was "really distressed" about the lack of progress. "I am ready to consider appropriate action if this dispute continues," she said.

The FCC says it can get formally involved in the dispute if one party filed a complaint that the other side wasn't negotiating in good faith, such as by not negotiating at all or not providing "considered reasons" for rejecting any aspects of an offer. CBS and TWC continue to negotiate, and neither has filed such a complaint.

Other organizations — New America Foundation, a think-tank whose board is headed by Google's Executive Chairman Eric Schmidt, advocacy group Public Knowledge and the Sports Fan Coalition — also have spoken out in support of limiting or banning future TV blackouts. The organizations held a conference call for reporters that was sponsored by American Television Alliance, which is largely funded by cable and satellite TV providers.

Sports, which is the most sought-after programming on cable, has become a rallying point for proponents of a quick resolution. Several NFL pre-season games on CBS were blacked out in the affected markets.

"Sports should be exempt from the takedowns," said Scott Weiss, New York/Tri-State Chapter chair of the Sports Fan Coalition. "We'd like to see sports shows put back on air. The FCC should get involved to make sure fans don't get hurt in these disputes."

CBS and TWC have largely agreed on the fees, but the negotiation now focuses on the issue of digital rights. TWC is seeking to reclaim the terms it had in the expired contract. CBS wants to rework them to reflect the fact that it now negotiates separately with several companies that stream its shows online.